I have two very tiny rust spots in the typical rear quarter meets rear bumper spots on my Honda S2000 (Silverstone metalic). The one is pretty much limited to the lip where that god awful black trim piece use to be. The other is about the size of a dime in the same area and does not appear to have made it to the pinch weld in the rear quarter yet. I really want to try to get these things before they get to the pinch weld and potentially get behind the rear quarter (who knows maybe they already are). This car is really just a fun toy that will see track duty, so spending tons at a body shop only to potentially mess it up on the track is not what I am after. That said the rear quarters are not replaceable and I would like to put an end to these two small spots.

My plan of attack:

Expose all of the rust by removing paint until I see clean metal. knock out as much of the rust as possible with a dremel and light sanding. Hopefully by this point I will be limited to the lip and just upon to the outside of the rear quarter in the one spot and the lip and a quarter size area on the other. From here I am going to use loc-tite rust converter as opposed to a POR 15 due to the fact that rust will still be present and it is my understanding that POR 15 does not do as well as a converter in these situations. Lastly I will use OEM touch up paint in a airbrush to detail spray the tiny areas, really trying to limit the total surface area impacted (a rattle can would just not be fine enough).

My concerns:

1. POR 15 would work better. I have read tons of great reviews on POR 15, but I read many articles that suggest a true converter like the loc-tite is best when you cans go to clean metal and I can't. That said the loc-tite is a bit scary in that it implies that if you don't leave rust you could cause rust. I have just read so many different opinions, I think I will just pull the trigger on the loc-tite, especially since I have a bottle on hand. Unless someone makes a convincing argument (someone with experience in both).

2. Can you spray OEM touch up in a airbrush without diluting it? I read it may need diluted to spray well. What do I use and how much? Honestly if I can't use the airbrush I will likely just brush the touch up on, as a rattle can will be way to big of an area and taping that tight will leave a huge paint line.

Any thoughts from paint experts?

Its rusting from the inside out. So unless you are going to cut the metal out and back to clean metal and weld a patch in the rust will return. Rust in those areas starts because the outter panel is welded to the inner wheel well and moisture/dirt/salt gets trapped there and eats a hole in the metal. Once you scrape the paint off there will be rust holes there.

Kinda my fear, which is why I was taking the approach I was with just leaving the rust, using a converter, tossing some paint back on, and hoping to slow it down. I don't drive the car in the winter, rarely in the rain, and it is kept in a heated garage (unfortunately the previous owner did just the opposite). It is really just a track/fun car that I got for a good price. Realistically something will happen to it over the course of tracking it or I will widen the fenders over the course of the next few years. I just wanted to slow it down a bit and make it look nice for the time being. I can also access the backside well enough to spray regular treatments of zebart in to try to slow it further.

What I don't want to do is make the rust worse OR get in way over my head trying to get cute with the airbrush. So if I am going to do any of that please let me know and advise how to proceed.

Thanks!!

He's right, it needs to be cut out. POR is more marketing than science, but if you don't want to do the full repair, which I totally understand, then sure just grind down the rust, POR it or use a polyester filler, then airbrush it. It won't look any worse than it does now. You might get a year out of it before bubbling starts again.

Thanks guys! Well maybe I will get lucky and it will just keep bubbling in that same spot. If not I figure the permanent fix will always be an option in the future.

Any thoughts on how to water down the OEM paint to make it thin enough for an airbrush? Acrylic lacquer? There is also a store nearby who blends paint for spray cans, I suppose I could see what they could do. The painting worries me the most, I intend to practice before I do my car, but I have zero experience.

It probably won't look right if you spray it with an airbrush. You might be able to get it close enough, but the tip size is so small on an airbrush that the metallic pattern is a lot tighter/more concentrated. It will work, just don't expect it to be a seamless blend.

You can use regular urethane reducer if it standard automotive urethane paint. If you are using a factory touch-up bottle, it is usually enamel and normally uses an enamel reducer. You would want to check with the supplier of the materials to make sure you get the right reducer/thinner.

If you remove as much rust as possible and seal up any holes with fiberglass reinforced filler - you should get at least 1 - 2 years when stored indoors, possibly much longer. It's storing outdoors and driving through rain, mud, or salt that really does damage to body panels.

Isn't an Epoxy primer better than POR15?

Yes, epoxy is better. POR is a single component moisture cured urethane...

So what the general consensus seems to be is to remove the rust as opposed to converting it with a converter and then to use like a fiberglass reinforced bondo. From there coat with an epoxy primer and top it off with paint? My only fear with this approach is that I could get in over my head with the removal/filling. I guess my though was by using a converter I can keep it simple and the area as small as possible, heck maybe even small enough to use the touch up paint with a brush. It doesn't need to be fancy, just as good as reasonably possible for someone with no body work experience. And if the rust comes back I can always take it to a professional and not really be out much, except a bit of time.

You could scrape the rust off and get to the inside of the panel and pour rust converter in there to neutralize it then just brush on some touch up paint. That will slow it down.